Nearly all the light that strikes an opaque object will pass through and cast a shadow

It’s a false statement.

Explanation:

An object which does not allow to pass light through is called as opaque object. It creates a shadow when light falls on it.  While transparent object does allow to pass light though it and does not create shadow. From the above definitions, it is cleared that the given statement is false.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.